Haidong Wang1,2, Chenglin Liu 1,2,*, Kaixuan Liu 3, Guangkun Yang1,2, ZHANG Xue1,2, Tong Qiao1,2,
[1. State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China; 2. College of Geosciences, China University of Petroleum, Beijing 102249, China; 3. Research Institute of Exploration and Development, PetroChina Changqing Oilfield Company, Shaanxi Xi’an 710018，China]
Abstract：Helium-rich natural gas has become an increasingly important target for resource exploration, yet the geological processes responsible for helium accumulation are still not fully constrained. A notable feature of many helium-bearing gas reservoirs is the simultaneous enrichment of helium and molecular nitrogen, which provides an important clue for understanding helium migration and preservation. In this contribution, gas geochemical characteristics are combined with reservoir accumulation analysis to discuss the origin of the He-N2 association and its controlling mechanisms. The results suggest that helium and nitrogen are generally derived from different source systems and formation processes; therefore, their enrichment in the same reservoir is unlikely to be a simple inheritance from primary gas generation. Instead, helium released from radioactive decay and nitrogen related to nitrogen-bearing components may first be transported by basement- or formation-related fluids. During later gas-water interaction, both gases can be transferred from the aqueous phase into the free gas phase because of their low reactivity and broadly comparable behavior under reservoir conditions. Subsequent modification of the gas reservoir, including methane loss through diffusion or seepage and the consumption of chemically active components, may further raise the relative proportions of helium and nitrogen. These processes together form a coupled enrichment pathway in which fluid-mediated transport, gas-water phase transformation, and selective loss of other gases play key roles. This study provides a conceptual explanation for He-N2 co-enrichment and offers a useful framework for evaluating helium-rich natural gas reservoirs.
Keywords:Helium-rich natural gas; Nitrogen; Coupled enrichment; Gas-water interaction;Gas loss; Accumulation mechanism
Author Profile (first or corresponding author):
Wang Haidong, Male, PhD candidate, mainly engaged in helium accumulation mechanisms and helium-
rich natural gas reservoir geology. E-mail: 2022310042@student.cup.edu.cn
